Drilling fluid



United States Patent 3,524,813 DRILLING FLUID Jack H. Kolaian, Houston,Tex., assignor to Texaco Inc., New York, N .Y., a corporation ofDelaware No Drawing. Filed Apr. 25, 1967, Ser. No. 633,432 Int. Cl. Cm3/14 US. Cl. 252--8.5 9 Claims ABSTRACT OF THE DISCLOSURE An aqueousdrilling fluid dispersant and a method of drilling wells using saiddrilling fluid which contains a substituted hydroxyacetophenonedispersant, namely, 2,4-dihydroxyacetophenone, 2hydroxy-S-methylacetophenone and mixtures thereof.

This invention relates to a novel aqueous drilling fluid for drillingwells through sub-surface formations by means of well drilling tools,and particularly to such an aqueous well drilling fluid having improveddispersibility as a result of containing therein a novel dispersant ashereinafter more fully described. The invention is also concerned with amethod of drilling wells employing the novel aqueous drilling fluid.

Drilling fluids, or muds as they are sometimes called, are slurries ofclayey solids used in the drilling of wells for tapping undergroundcollections of oil, gas, brine or water. Such fluids have a number ofdifferent functions, the most important of which are to assist in theremoval of cuttings from the well, to seal off formations of gas, oil orwater which may be encountered at different levels, to lubricate thedrilling tool and drill pipe which carries the tool, and to hold thecuttings in suspension in event of shut-down in drilling.

An ideal drilling fluid is a thixotropic colloidal system, i.e., a fluidwhich on agitation or circulation (as by pumping or otherwise), has ameasurable relatively low viscosity and is free flowing (not plastic),particularly at high temperatures; but when such agitation orcirculation is halted, the fluid sets or gels. The rate of gel formationis such as to permit the cuttings to fall only a short distance beforethe gel structure is sufiiciently strong to support them.

When such a drilling fluid having the proper viscosity, the proper gelrate and proper gel strength is circulated through a well bore, it has asufliciently high viscosity to carry the cuttings and sand from thebottom of the hole to the surface and it has a gel rate such as to allowthe cuttings and sand to settle in a settling pit. On standing in aquiescent state, it develops suflicient gel strength to prevent thesettling of the cuttings, sand or weighting material, etc., in the wellbore when it becomes necessary to discontinue circulation for anyappreciable period of time. Such a fluid is also characterized by itsability to form a mud cake on the borehole wall, thereby assisting insealing off the traversed formations and inhibiting socalled water loss,i.e. loss of water from the drilling fluid.

One of the principal problems in mud chemistry is the production ofsuitable drilling fluids having satisfactory dispersibility, and thenecessary thixotropic properties discussed above.

In accordance with the present invention the problems of dispersibilityin aqueous drilling fluids can be solved by 'ice incorporating in anaqueous drilling fluid a substituted hydroxyacetophenone having thegeneral formula wherein A is hydroxy or hydrogen, B is methyl orhydrogen; wherein when A is hydroxy, B is hydrogen, and when A ishydrogen, B is methyl, including mixtures thereof, said substitutedhydroxyacetophenone being present in the drilling fluid in an amountsuflicient to reduce the viscosity thereof.

The term substituted hydroxyacetophenone as used in the specificationand claims is intended to cover any substituted hydroxyacetophenonemeeting the above general formula and having substituents of theprescribed type at the indicated positions on the ring and mixturesthereof.

More particularly representative substituted hydroxyacetophenones of thepresent invention include 2,4-dihydroxyacetophenone, 2hydroxy-S-methylacetophenone, and mixtures thereof.

It is known from the article appearing in Zhur. Priklad. Khem. 35, pages638-647 (1962), Organic Viscosity Reducer in Clay Solutions by D.Tischenko and S. Fleisher (CA, 57, 249lg, 1962), that theortho-dihydroxybenzenesulfonic acids, theortho-dihydroxy-alpha-toluenesulfonic acids and water soluble saltsthereof are viscosity reducing agents in clay laden drilling fluidswhereas the corresponding metaand para-dihydroxybenzenes including thecorresponding sulfonic acid derivatives and water soluble salts thereofare ineffective viscosity reducing agents for aqueous drilling fluids.

The substituted hydroxyacetophenones of the present invention may beadded to an aqueous drilling fluid in amount ranging from about 0.1pound to about 10 pounds per barrel of drilling fluid. In general, ithas been found that amoimts less than 0.1 pound per barrel do notproduce completely satisfactory results in terms of dispersing activitywhereas amounts above about 10 pounds per barrel are economicallyunattractive and no improved results are obtained therewith. A preferredrange for the substituted hydroxyacetophenones of the present inventionis from about 0.25 to about 5 pounds per barrel of drilling fluid formost consistent results and efficiency.

The substituted hydroxyacetophenones employed in the present inventionare known compounds and the manner of their preparation is known in theart.

In the table, gel strength (Gels) is reported as determined by ashearometer in accordance with the procedure in the American PetroleumInstitute publication RP-29,

results being expressed either as pounds/ square feet or as time inseconds for a tube to settle in the mud (after the mud has stood forzero time and for 10 minutes). If it settles in more than 60 seconds,shear is reported as pound per hundred square feet. Yield point (YP) iscalculated by subtracting the plastic viscosity (PV) from the Faunviscosity reading at 300 rpm. Plastic viscosity (PV) is obtained bycalculation, subtracting the Fann reading at 300 rpm. from the 600 rpm.reading. Apparent viscosity (AV) is equal to one half of the 3 Fannviscosity reading obtained at 600 r.p.m. The fluidity of a mud can beback calculated from these data, the results being expressed in Fannviscosity at 600 rpm. and 300 r.p.m. for a direct reading viscosimeter.

The properties of the base mud are shown in the table.

in the drilling fluid in an amount of from about 0.25 to 5 pounds perbarrel of drilling fluid.

5. In a method of drilling wells wherein a drilling fluid is passedthrough the well in contact with earth formations during the drillingoperation, the improve- The test data set forth in the following tableindicate 5 Infant which P contficting aid arth formations the advantagesof the substituted hydroxyacetophenone Wlth Z g g contammglclay Sohdsdispersants of the present invention and demonstrate the perse erem aslspersant east poun beneficial results of same in im rovin the disersibilit per barrel of dnnmg fluld of Substanna] hydroxyaceto f d fl pg p y 10 phenone selected from the group consisting of 2,4-dihy- 0 111gh 1 fd 1r fi d b th droxyacetophenone, Z-hydroxy-S methyl-acetophenoneRepresentative p YSKFQ propert eso r1 mg 111 s o and mixtures thereof.before and after addition of various materials including In a method asclaimed in claim 5 wherein the the substituted hydroxyacetophenones ofthe present 1nstituted hydroxyacetophenone is 2 4 i vention are shown inthe table. In each example the 5 pheuone amount of material or materialsadded to the base muds, 7 I a h d as l i d in claim 5 wherein the if y,are Shown, expressed in terms of Pounds of material substitutedhydroxyacetophenone is 2-hydroXy-5-methylper barrel of drilling fluid.acetophenone.

TABLE Shearometer gels Amount and lb./100 ftfl API type Ap vis. .L., Ex.Type mud di persant PV YP cpe 0 1 10 1 pH on Time, hrs.

1 LpH LOA {12 22 2 16 14 23 3. 7 7. 5 9. 5 15. s 16 2 LpH 0. 25B" 8 2018 0. 25 {12 17 2 20 12 16 2a LpH 1.013 9 16 0.25 {12 1s 2 17 16 1e 1LpHLow pH mud.

The data in the above table show that the substitutedhydroxyacetophenones of the present invention are effective dispersantsin aqueous drilling fluids.

I claim:

1. An aqueous drilling fluid containing clay solids dispersed thereinand as the dispersant from about 0.1 to 10 pounds per barrel of drillingfluid of a substituted hydroxyacetophenone selected from the groupconsisting of 2,4-dihydroxyacetophenone, 2-hydroxy-5 methylacetophenoneand mixtures thereof.

2. An aqueous drilling fluid as claimed in claim 1 wherein thesubstituted hydroxyacetophenone is 2,4-dihydroxyacetophenone.

3. An aqueous drilling fluid as claimed in claim 1 wherein thesubstituted hydroxyacetophenone is 2-hydroxy-S-methylaectophenone.

4. An aqueous drilling fluid as claimed in claim 1 wherein thesubstituted hydroxyacetophenone is present References Cited UNITEDSTATES PATENTS 1,999,766 4/1935 Lawton et al. 2528.5 2,333,133 11/1943Wayne 252- HERBERT B. GUYNN, Primary Examiner 2 3 UNITED STATES PATENTOFFICE CERTIFICATE OF CORRECTION Patent no. 36 M 3 Dated August 18, 1970Inventor(s) Jack H. Kolaian It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

COLUMN line 8, "substantial" should read --substituted--.

$125 3 SEALED OCT 2 0 @EAL) m I. mm, Jan Imam Weston of Patent: EdwardEmmi meeting O

